The Evolution of Common Sense

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Arthur Stanley Eddington was an interesting fellow. The English astrophysicist who photographed the solar eclipse that validated Einstein’s theory of general relativity was also a Quaker, a pacifist, and a clever popular writer. In his 1928 book The Nature of the Physical World [1] he began by noting that he had before him two tables: one of common sense, which was substantial and could change its essential nature if burned, and the table of science, which was insubstantial, mostly empty space, and which if burned changed only its state, not its essence.

Science, Eddington held, undercut common sense. By contrast, a half century earlier, Thomas Henry Huxley, Darwin’s defender and general polymath, wrote that science was "nothing but trained and organized common sense" [2]. What should we think about this? At least one Christian philosopher, Alvin Plantinga [3], has argued that this means that if evolution is true we should not think evolution is true, because our evolved cognitive capacities did not evolve to deliver us truth, but only fitness.

Darwin himself wrestled with that problem. In a letter to Belfast philosopher William Graham in 1881, not long before his death, he wrote [4]:

But then with me the horrid doubt always arises whether the convictions of man’s mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey’s mind, if there are any convictions in such a mind?

With philosopher Paul Griffiths [5], I call this the Darwin’s Monkey Brain Problem: how can we rely upon a cognitive apparatus which had not evolved for finding out about the world, but instead for the purpose of getting primates laid?

Mind, Darwin’s horrid doubt was not about science. Instead his horrid doubt was more transcendental: "Nevertheless you have expressed my inward conviction, though far more vividly and clearly than I could have done, that the Universe is not the result of chance". Unlike Plantinga, Darwin was in doubt about purpose in the universe. Plantinga thinks the exact opposite: that the monkey brain problem leaves us less certain of science and more certain about purpose and God.

The reliability of common sense is an issue for philosophers and cognitive scientists alike. Philosophers debate whether or not ordinary objects, the objects of common sense such as Eddington’s Table 1, can be said to be real or exist.

Famously among philosophers, George E. Moore argued that one could prove that there was a world outside the mind because we all know that we have a hand, and granting that, the world follows [6]. Of course, the existence of that hand itself was at issue. Ordinary objects are something we need to understand [7].

Philosopher Guy Kahane has addressed this issue in the realm of ethical skepticism, dubbing these sorts of arguments evolutionary debunking arguments or EDAs [8]. They have this structure:

Causal premise. S‘s belief that p is explained by X

Epistemic premise. X is an off-track process

Therefore, S‘s belief that p is unjustified

An "off-track" process is a process that fails to track truth. Evolution by natural selection tracks fitness not truth. Kahane rejects this argument against objective value. But does it mean the monkey brain problem still holds for science? Does evolution debunk our common sense and with it science? Are our beliefs about the world at risk?

EDAs can be leveled against belief in moral truths, religious claims and common sense beliefs. A pragmatist philosopher might say that if you can bark your shins on a table, it is real enough, as the saying goes, for jazz (the other common saying here ends "for government work", which should strike fear into the hearts of every bridge user). This amounts, though, to the the claim that so long as our beliefs contribute to our fitness, or at any rate do not detract from it, the reality of the objects we believe exist, the content of our beliefs, is irrelevant. In the end, Kant was right: we only know and make inferences from the appearances of things.

In assessing EDAs, though, it pays to ask what is fitness for – what is it that gives a belief any fitness? In the case of moral values, fitness is clearly at least in part down to our behaviour being acceptable to those around us, so that we do not suffer sanctions, and gain assistance when we need it. We are adapted to interpersonal and social interactions.

In the case of religious claims, as Griffiths and I argue, our beliefs are more likely to be fitness enhancing for much the same reasons as moral beliefs – they avoid our being censured, perhaps even executed as apostates or heretics, and increase our likelihood of receiving aid when we are in dire straits [9]. These are vulnerable to EDAs because our best account of why they enhance fitness has nothing to do with the truth of the content of the beliefs.

But this need not be the case for every belief. It seems likely that some beliefs – let us call them environmental beliefs – gain fitness because they track, if not exactly truth, then satisfactory ecological correlations. Obviously, if you believe there is a cliff in front of you, and there is, then you will tend not to leap over it, and your fitness is thereby enhanced. If you believe that rustling in the undergrowth is a leopard, and take evasive action, you are fitter than the poor thinker who takes a Plantingan line and treats it as a mere Kantian construct. Hume had Cleanthes invite Philo to take his skepticism seriously by leaving via the upper floor window [10]; an overzealous skeptic would be very unfit indeed.

Willard Van Orman Quine, the famous American philosopher, put it thus:

Creatures inveterately wrong in their inductions have a pathetic, but praiseworthy, tendency to die before reproducing their kind. [11]

I do not know how praiseworthy it may be, but if you get things wrong, you can end up not reproducing. Environmental beliefs are, as much as anything, truth tracking, but this is no guarantee that the environmental beliefs we do have are therefore true. They merely need not to kill us on average.

Statisticians refer to two kinds of errors: Type I (false positives) and Type II (false negatives). A false positive may not kill us, but there is a cost to every belief, and believing that, for example, that it is bad luck to walk under ladders takes time and extra effort, which can reduce fitness. Believing that the rustle in the undergrowth is a fairy rather than a leopard (a false negative), can have dramatic costs.

We cannot know everything: we are rationally bounded by our computational, memory and time constraints. We are not cognitively omniscient or ever free from error, so we must trade off Type I against Type II errors [12] and seek to live on that basis.

Organisms have to act, and so they must do so on limited information. The end result is that species with nervous systems like us evolve typical cognitive mechanisms that operate correctly in their usual environments. These have been named as Umwelten, or "sensed environments", by Jacob von Uexküll, an Estonian ethologist [13]. An Umwelt is what aspects of their environment organisms typically respond to. Uexküll used the example of a tick that reacted to gradients of light, butyric acid, and warmth. These things indicated the presence of hosts or opportunities to attach to hosts, and were all that the tick needed to, in our terms, "believe".

The common sense world of ordinary objects like Eddington’s Table 1 is, in effect, the Umwelt we all share. It signals facts about the world we need to have beliefs about that are reliable and which we therefore have some reason to think are true.

In fact, I would say that our Umwelt is the shared Umwelt of all primates, and which is similar to that of many middle-sized vertebrates (ignoring birds that can see in ultraviolet, bats that can echolocate, and magnetotactic animals that use the earth’s magnetic field to navigate). We are primates, and primates evolved to deal with a world of geography, trees, fruit, other organisms and each other. The monkey brain is not so much a problem as it is an environmental truth tracking device.

In short, common sense is the primate Umwelt. The reason why we all share it, or have access to it (if we do not suffer from a cognitive deficit) is that we inherited it from our predecessors, quite literally, because they did not die in the use of it before they reproduced.

But this still doesn’t validate scientific beliefs. Science is not really organized common sense. It is refined, revised and rejiggered common sense. The ordinary objects of common sense, like Eddington’s table of substance, are not the ultimate objects that science tells us exist, even if we do not think that scientific realism is a viable view [14].

On no construal of common sense can many of the objects of common sense be defended in the light of science. A substantial table relies on a common sense metaphysics, formalized in Aristotle, that the world is comprised of substance that takes up space and is organized into objects by form, a view called hylomorphism from the Greek for matter+form. Modern physics dismisses this metaphysics, although philosophers seem reluctant to follow.

So, how do we get to scientific beliefs from common sense? The answer is to see science as bootstrapping upon common sense. There is enough truth tracking going on in common sense for us to start revising our beliefs and observations without prior theory [15]. Science takes the objects of experience as explicanda, things that stand in need of explanation. Our Umwelt itself stands in need of explanation – why is our sensory world useful enough to help us survive and reproduce? The answer is given above, a sketch of a scientific view.

In the end, beliefs that track truth come in degrees of validity and accuracy. It is not all-or-nothing, and so long as we do not die before reproducing our kind, that may be good enough for government work.

8. Kahane, Guy. 2011. Evolutionary debunking arguments. Noûs 45 (1):103–125 [PDF]. For an analysis of EDAs, see this series by John Danaher.

9. This is the account of religion as the "honest costly signaling" of commitment and hence community engagement; See Dow, James W. 2006. The evolution of religion: three anthropological approaches. Method and Theory in the Study of Religion 18 (1):67–91; and Sosis, Richard and Candace Alcorta. 2003. Signaling, solidarity and the sacred: The evolution of religious behavior. Evolutionary Anthropology 12:264-274.

About the Author: John S. Wilkins has a PhD in the history and philosophy of biology, and is an Associate of the philosophy department at the University of Sydney. He works on evolution, taxonomy and religion, and has a blog, Evolving Thoughts.

The views expressed are those of the author and are not necessarily those of Scientific American.

In day today life we deal with each other with commonsense,at that time we don’t need to consider we are involved from lower animal.Same is true that universe born with big bang. The evolution of commonsense developed from our daily need. our mundane requirement.Scientist are also used common sense for day today dealing only when they work in laboratory they think about scientific truth

Unfortunately, common sense does not show up often enough in government work and science appears to be right out given the anti-science bias of many politicians.

We have seen video of and read about non-human primates making common sense decisions and it makes me smile to think about my monkey brain. Thank you for a too rare combination of evolution and philosophy.

I have read this several times and remain unenlightened as to the point of the article or the authors opinion of commonsense. One reason I have little interest in ‘philosophy’ in it’s own right is that philosophers can use many words and communicate virtually nothing. A previous article in Sci Am, from some years back, noted that the human brain (and presumably other, similar brains) have no mechanism for discovering and ferreting out false positives, thus false beliefs (which do not preclude procreation) tend to accumulate. They become social and cultural beliefs and traditions when they are adopted by social groups, and tend to bind social groups closer together, giving the more closely bound group an advantage over other, less closely bound groups. Yet false beliefs are still false, even when they bear the label ‘common sense’, thus we can conclude that common sense may be either true or false – the fact that it (common sense) is a belief is of no use in determining which. The scientific method is the only reliable mechanism we have created which can winnow false common sense beliefs from true common sense beliefs. In my experience and opinion, ‘common sense’ is the last refuge of dogmatists, the superstitious, or of fools.

I enjoyed this article. It reminded me that the way people think, and the practice of science are not the same thing. It is a monumental challenge for us to overcome our "common sense" in trying to understand the world. If we are to do "good" science we need to remain aware of this challenge and the impact it might have on our thinking.

Common sense may refer to many things or rather aspects. One is the existence of the macroscopic objects that we assume, tables, animals and the like, and that they are as we think they are. Why do we live in Kant’s phenomenal world? Well, the answers are many. If our perceptions of which objects are phenomenally there did not to any degree coincide with what is there – given that the argument from illusion is not true – we would have been eaten by lions, whom we then could not perceive, many thousand years ago. Moore’s Hand-argument is a nice one, for who can actually believe he does not have a pair of hands, given that he or she is, as we say, normally equipped and has not been in a major accident? In physics one does not debate the existence of physicists. I think even Niels Bohr believed he wrote papers. Such things are taken for granted in a common-sense sense. Given the existence of a natural world one can construct a series of arguments having to do with our perception, how it works, what it perceives and does not perceive (such as radio waves) and so on. One then finds a rather nice evolutionary fit. The rest is the argument from illusion, or various forms of it, which are not only from a common sense point of view ridiculous, but also impossible to prove in themselves. There are of course various forms of common sense which are not to be taken as granted as the existence of tables and lions, such as personal and cultural prejudices, but that is another matter. So, the philosophical usages of the term common sense depart from the everyday usage of the same term, something that should be pointed out to avoid misunderstandings. – One interesting aspect, however, is why we are wired so as to perceive or conceive causality among our perceptions. Do causes exist? We perceive ourselves a having free will, or incentive. Why? Are they performance-enhancing illusions or are they real?

I’ve been interested in this subject for years, and this article stimulates some thoughts. The first is, we know that we can depend on our scientific minds because, when we build bridges, they stay up (with a few notable exceptions). And for those that don’t stay up, engineers and scientists figure out why and use that to help our scientific understanding evolve. Our common sense then learns to ask an engineer trained in making bridges when we want a bridge built.

Another thought is that our commonsense understanding of the universe is not at all based on "convictions of a monkey’s mind". When we are young we figure out the rules of the universe on our own somewhat independently of what our parents figured out. We climb trees, build towers of blocks, pour water from one shape of container into one with a different shape, throw things, etc. There are only a few things that are hard-wired, and those tend to be things that are invariant and can be lethal, such as a fear of jumping off cliffs or being left alone by parents. Even those fears can be overridden by experience. Many social scientists refer to children literally as scientists exploring the rules of the universe by means of play. The more we play, the more we explore, the more our understanding is refined, so learning logic and math at an early age is incorporated into the rules of the universe that we are creating. So we are not depending on monkey brain to understand the universe, we are depending on monkey brain to use our experience to create a set of rules to understand the universe.

At the same time, children get a lot of information from parents, but not the rules of the universe. Parents can provide the tools needed for figuring out the universe, such as toys, games, playgrounds, museums, sports, etc., but children use them to figure out the rules themselves. Adults also provide social rules, explanations, rationalizations, definitions, language, etc. That is where religions or superstitions enter the picture. Children don’t learn the color of the sky from their parents, but they do learn the word for that color, and if they ask "Why is the sky blue," they may get nonsense or fables or science as an answer, but the sky is still what they perceive. And children, by the way, are very good at figuring out when adults are BSing them. That is an important survival skill.

This article makes the same mistakes that Darwin made in Origin. It makes statements that seem to make sense, until subjected to close scrutiny. Darwin arrived at the term Natural Selection from study of selective breeding of specific characteristics. Darwin called it selection, then applied the analogy to nature and called it Natural Selection.

The analogy was valid, but the correct direction for the analogy was from the natural process to the unnatural use of that process that added a critical factor, a breeder selecting which individuals bred. Darwin drew the analogy in the opposite direction. He attributed to nature the factor that did not exist in nature. That made him miss the only factor that did exist in nature capable of working on individual differences to create change in the species, the effect of external conditions.

Darwin deliberately decided to exclude the effect of external conditions. Instead, Natural Selection resulted from variations that gave individuals internal qualities that favoured them in struggle for existence involving competition for scarce resources.

Darwin acknowledged that did not explain how species adapt to specific conditions. In ch. 3 he argued that, despite appearances, species did not adapt because of the effect of external conditions, but because they were favoured in those conditions. What favoured them in those conditions? You are asking too many questions.

Quine wrote about creatures having inductions, but the evidence is that brains did not evolve to have inductions. They evolved to have behaviours that worked. In the case of mammals, they learn most of those behaviours by observing and absorbing them from those who had used them and survived. Those that did not work did not survive.

The evidence is in the lack of innovation of the large human brain until the change from the hunter gatherer lifestyle around 10,000ya required humans to change how they used the brain.

Darwin developed Laws and wrote as if they determined outcomes, when the reverse is true. Ernst Mayr wrote that biology cannot have laws like those in physics, only concepts. So again, Darwin applied an invalid analogy, this time from physics to biology.

Most present day biologists accept that external conditions drive species change, but they still call it Natural Selection and continue to apply assumptions that are based on Darwin’s version of Natural Selection, which excluded the effect of external conditions.